Starting Session takes really slow - notebook session Microsoft Fabric

Was any solution/advice for this issue offered?

I'm seeing the exact same thing. A simple "Hello World" notebook using the default workspace environment will start a spark session in approx 4-5 seconds. Creating a new environment to add a custom library and setting it as the workspace default results in the same "Hello World" notebook now taking just over a minute to start a spark session.

This doesn't appear to be "Network latency, Regional Differences, browser issues, or temporary Fabric service hiccups..." as the difference in startup time can be reproduced with 100% reliability simply by switching the environment back and forth and re-running the same test notebook.